Computational fluid dynamics (CFD) is a common approach for improving the understanding of hydrodynamics, thermodynamics, and chemical kinetics of a flow system. CFD codes have been evolving over the past 20 years with great advances in both the numerical techniques and computer hardware. CFD applications have been extended from simple laboratory-type problems to complex industrial-type flow systems. Computer simulation has gained widespread acceptance as an effective and cost-saving tool to further improve the performance of flow systems.
One CFD application is in the area of petroleum/catalyst flow in a fluidized catalytic cracking (FCC) reactor. Since the introduction of commercial-scale FCC systems in the early 1940s, the FCC process has been constantly improved and has become the primary conversion process in the modern refinery industry. In improving the process, cracking reaction time in an FCC unit has been substantially shortened and the hydrodynamic effects on cracking processes have become better understood. It has been suggested that a fundamental understanding of the hydrodynamics and heat transfer in the injection zone and riser is critical to the development of higher performance FCC units which would not only increase the competitiveness of the refinery industry, but also reduce pollutant emissions into the environment.
Various computer-implemented approaches have been developed for the purpose of improving FCC performance. One such approach has been developed at Argonne National Laboratory for simulating a three-phase (gas, liquid and solid) flow in FCC riser reactors. This computer code, referred to as ICRKFLO, uses a sectional coupling, time integral approach to handling cracking flows, including heat transfer between solid, liquid and gas; vaporization of the oil droplets; oil cracking; and coke formation. The time integral approach couples hydrodynamic and kinetic processes in a way that prevents the calculation from becoming numerically unstable. The ICRKFLO approach does not provide local kinetic model constants, as opposed to global model constants, which are necessary for computing reaction and product yields in non-uniform flow fields under a broad range of operating conditions for a reactor system. The inability of the ICRKFLO approach to provide these local kinetic model constants has precluded the consideration of the local fluid dynamic effects on the extracted local kinetic constants for each particular application system to which the methodology is applied. This has limited the capability of this approach in modeling and controlling FCC processes.
The present invention addresses the aforementioned limitations of the prior art by providing a methodology for extracting local kinetic constants for computing reaction and product yields under a broad range of operating conditions, such as for example in non-uniform flow fields in a FCC reactor system. The inventive approach implicitly includes the local fluid dynamic effects in the extracted local kinetic constants for each particular application system to which the methodology is applied.